For on site testing it is essential to minimise the amount of reagent handling. This can be achieved by using a compact sampling and assay device that contains all the necessary reagents needed for performance of the assay. In many assays, two or more reagents may be used that are combined just prior to, during or after sampling. To fulfil these needs compartmentalised structures with separate reagent reservoirs have been introduced. Several sample preparation and assay devices have been developed for various types of analysis that are aimed for facilitated sampling in both laboratory and non-laboratory environments. Such devices are disclosed for example in U.S. Pat. No. 6,524,530, U.S. Pat. No. 5,905,029, WO-95/25948, WO-99/31218, U.S. Pat. No. 4,770,853, U.S. Pat. No. 4,353,868, WO-97/03209, WO-97/23596 and US-2003/0186458.
All the above mentioned prior art documents disclose sampling and assay devices which comprise the following components: A sampling swab, a tubular container closed from one end, and within this system two or more separate reagent chambers separated by partitions. There are, however, differences in the technical approach of the mechanisms in how the reagents are released and brought into contact with each other and the sample.
A sample collecting member and wiping inspection instrument described in U.S. Pat. No. 6,524,530 is a compact device with a sample wiping member and two partitioned reagents. The sample is first introduced with the extractive reagent in the first container by forcing the swab of the sampling element downward through a seal material. After bacteria adhered to the swab have been extracted the extractive reagent is brought into contact with the reactive reagent by braking the partition of the reagent container by the upward movement of the container relative to the main body of the sampling and assay device. The extracted bacteria flow with the extracting liquid down into the reactive reagent container. In another embodiment of U.S. Pat. No. 6,524,530 a reagent container is upwardly press moved to rupture a seal by the lower end of a breaker followed by a downward movement of the wiping member to rupture the next seal material further followed by a downward movement of the main body to rupture the next seal material by the upper end of the same breaker as above. The document also discloses bacterial detection by a colouring reaction. Moreover, the document discloses that the seal materials are successively tear broken.
U.S. Pat. No. 5,905,029 discloses a method for rapid hygiene testing by detecting ATP in biomass by using a luciferase/luciferin bioluminescent reaction. The document discloses a vial system which uses a series of vials containing necessary reagents and an all-in-one swab device which provides both the swab and the reagents. The luciferace/luciferin may also be isolated in a separate chamber which can be broken to expose the luciferace/luciferin to the buffer solution sealed in another chamber. The buffer solution is released by squeezing the tube.
WO-95/25948 discloses a sample collecting and assay device comprising a tube having a removable top closure on which is mounted an elongate swab. The tube contains one or more reagent compartments separated with frangible membranes. According to the invention two or more compartments can be used, where the base of one compartment may be defined by the top of another. The membranes are successively broken by movement of the swab, or a coaxially-extending blade-like member.
An assay device disclosed in WO-99/31218 comprises a sampling swab and two reagents defined by frangible membranes into separate compartments on top and bottom of the tube. The top reagent may be released by a single operation into the tubular member by relative movement of the two top pieces. The frangible membrane separating the bottom reagent is broken on a movement of the bottom part relative to the tube. The target component in combination with reagents in the compartments undergoes a reaction and gives a detectable signal. The device is suitable for detection of micro-organisms obtained by swabbing. The colour produced is visualised through a window and can be compared with a standard. The standard is in the form of reference spots on the device and give a quick indication of the concentration of the analyte in the sample.
U.S. Pat. No. 4,770,853 discloses a compartmentalised sample collecting device with reagent containing sealed chambers and a solid phase immunodiffusion assay area where the presence of the analyte in a sample can be visualised by the naked eye. The device is intended for self contained solid phase immunodiffusion assay which is also based on the breaking of the seals by the sample collector. By an arrangement of nodules and grooves within the test system the contents of a series of independent reagent compartments can be mixed in a stepwise manner.
U.S. Pat. No. 4,353,868 discloses a specimen collecting and transporting device without any analyte determination property. The device includes a swab in a container connected to a closure cap, and a reservoir containing a liquid culture-sustaining medium sealed in a chamber. The seal is broken by the projection of the container when the container is moved relatively toward the reservoir, for example by striking the bottom end wall on some surface, such as a table top and axially or longitudinally move the container relative to the reservoir. The bottom container opening is covered by an absorbent pad which is in contact with the swab tip. When the device is inverted or tilted medium is placed into fluid communication with the absorbent pad allowing controlled or metered flow of the medium through it to the specimen carrying swab tip.
WO-97/03209 describes a test apparatus, system and method for the detection of test samples which includes a probe containing a swab and three compartmentalised reagents within the test unit separated by puncture membranes. The membranes are punctured consecutively by the downward motion of the probe allowing the test sample and the test reagents to react together in the test unit.
US-2003/0186458 discloses an assay device comprising a sampling wand having an internal reservoir which is introduced into a reaction chamber having two portions separated by a frangible seal. Introduction of the sampling wand into the reaction chamber causes rupture of a seal in the sampling wand releasing the reagent in the internal reservoir. Further movement of the sampling wand causes the frangible seal in the reaction chamber to be ruptured allowing the reagent to contact a reactant disc.
Other prior art documents disclose slightly modified solutions from those discussed above. For example a sampling and assay device as described in WO-97/23596 introduces a cap-shaped shuttle that assists the swab in rupturing the partitions between the reagent compartments.
Various purposes of the known devices are to provide an enhanced contact between the sample and the reagent, to determine the analyte in the specimen and, alternatively, to sustain the specimen during transportation. The above-mentioned documents disclose devices where either the swab itself or a rupture member pushed together with the swab is used to rupture the partitions separating the chambers. The design of those penetration means are such that they penetrate the seals in a consecutive order releasing the content of the reservoir into the next one.
There is a need to further improve available assay devices to enhance the test procedure.